This application is the national phase under 35 U.S.C. xc2xa7371 of prior PCT International Application No. PCT/JP97/01596 which has an International filing date of May 13, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
The present invention relates to a thermoplastic elastomer composition powder, and a molded article produced by molding the same.
Hitherto, a sheet-like molded article having a complicated uneven decorations such as leather grain, stitch and the like, on its surface has been used as a skin material of automobile interior parts. As the molded article, there has been proposed a molded article which is obtained by powder-molding a powder prepared by grinding an olefin based thermoplastic elastomer, as a substitute of a conventional vinyl chloride molded article (see, for example, JP-A-3-199579 and JP-A-3-199589). However, the molded article which is obtained by powder-molding the powder prepared by grinding the thermoplastic elastomer, had such a problem that when a molded article having a complicated shape, for example, such as a molded article having narrow and high convex portion, is produced, appearance faults such as pinholes, wormholes and the like, arise at the edge of the convex portion. Furthermore, there also arose a problem that when the molded article is released from a mold on production of the molded article or when the molded article is preformed before the molded article is laminated on a base material, the bent portion of the molded article tends to cause whitening because whitening is liable to arise on bending, Therefore, there is desired a thermoplastic elastomer molded article capable of making use of a feature of powder molding, wherein no appearance deficiencies arise and whitening does not arise easily on bending.
The present inventors have intensively studied about a thermoplastic elastomer powder which gives a molded article having excellent appearance regardless of a complicated shape and not whitening easily on bending. As a result, the present inventors have found that a powder having a specific property of a thermoplastic elastomer composition comprising a polyolefin resin and a specific hydrogenated diene copolymer in a specific ratio, causes no poor appearance and gives a molded article which scarcely causes whitening. Thus, the present invention has been accomplished.
According to the first gist, the present invention provides powder of a thermoplastic elastomer composition comprising (a) 100 parts by weight of a polyolefin resin; (b) 5 to 250 parts by weight of a hydrogenated conjugated diene based copolymer; and (c) 0 to 500 parts by weight of an ethylene-xcex1-olefin copolymer rubber, wherein a sphere-reduced average particle diameter is not more than 1.2 mm and a bulk specific gravity is not less than 0.38. The powder is used in the powder molding method, and gives a molded article which does not cause appearance deficiencies such as pinhole, wormholes and the like at the complicated shape portion such as a edge of the convex portion and scarcely causes whitening on bending.
According to the second gist of the present invention, the present invention provides a molded article produced by molding the thermoplastic elastomer composition powder described above. The molded article of the present invention does not cause appearance faults such as pinholes, wormholes and the like at the complicated shape portion and scarcely causes whitening on bending.